Camera settings to simulate miniature scale model
The best way to do this is just to find the real life values - as a ballpark, try scaling your model down to the 'model' size that you want, somewhere in the order of 10cm. You might want to adjust the blender grid and unit settings to make this easier to work with. The only other thing left to do is choose an aperture.

Generally photographers might use a wide aperture (low number) to get this effect. Start from 2.8 and see if it is too much/not enough. From there, adjust the focus distance, aperture and model scale to fine tune the result.